1. Field of the Invention
The present invention relates to a disc type recording medium on which additional data is recorded by forming disc tracks, and more particularly, to a method of recording additional information by forming groove tracks or land tracks in a disc in wobble formats and a storage medium for recording the additional information.
2. Description of the Related Art
A variety of data modulation methods can be used to form tracks on a disc type recording medium. For instance a disc track can be formed by modulating physical address information in a wobble format using binary phase shift key (BPSK) modulation. The address information is then obtained by demodulating a wobble signal according to a signal detected at the formed track.
FIG. 1 is a block diagram illustrating a structure of a conventional track forming apparatus for explaining a method of recording an address and additional information on a disc track. The apparatus of FIG. 1 includes a modulation unit 110, a carrier signal generation unit 120, and a disc track forming unit 130.
The modulation unit 110 modulates a carrier signal, which is generated by the carrier signal generation unit 120, by multiplying the input address and additional information by the carrier signal.
A modulation signal corresponding to the modulated address and additional information is input to the disc track forming unit 130. The disc track forming unit 130 forms a wobble corresponding to the input modulation signal on the disc track. The modulation unit 110 modulates the carrier signal using the BPSK modulation based on the address and additional information, and forms the modulated carrier signal on a disc track in the form of a wobble. As a result, a wobble signal having the same shape as the modulated carrier signal can be detected from the disc track.
FIG. 2 illustrates the BPSK modulation used in a conventional disc track forming method. As is apparent from points {circle around (1)} and {circle around (2)} shown in FIG. 2, information such as address information is read by reversing the phases of various portions of a wobble into which the address information is to be inserted. However, reversing the phases causes discontinuities of the wobble signal at the points {circle around (1)} and {circle around (2)}. The discontinuities of the wobble signal negatively affect wobble signals detected along adjacent tracks, causing signal deterioration and harmonic noise.
FIG. 3 illustrates a structure of a data frame recorded on an optical disc, the data frame comprising N sync frames which contain address information and/or other additional information such as disc recording conditions and copyright protection policies for disc access.
In an optical disc, data access is rendered in data frame units. As is shown in the data frame of FIG. 3, the address information as well as other additional information is expressed with p address units and repetitively recorded R times to increase the reliability of the information. Here, the length of an address unit corresponds to the lengths of n sync frames. In general, the address unit is a base unit for recording the address information and other additional information in a data frame containing 1-bit information. In this disclosure, it is considered that an individual data frame has its own address value and is a basic data unit for data access, and an address in pregroove (ADIP) is a basic unit for expressing information.
Use of discs in portable appliances such as mobile phones necessitates the miniaturization of optical discs. In these miniaturized discs, information of data frame length is recorded on two tracks along the circumference of a particular track of a disc, e.g., the innermost track, and the track length is shorter than a data frame length. When this occurs, an optical disc is likely to have a radial discontinuity. The discontinuity results in errors at at least two points of a data frame, thus remarkably reducing the rate of detecting the address and other additional information recorded in the data frame.
As described above, in the case of a conventional wobble formation method using BPSK modulation, discontinuities of the wobble signal are caused when reversing the phase of the wobble to record information such as address information in the wobble. Also, when forming a disc track using a data frame in a conventional format where the data frame is longer than a particular disc track, the optical disc develops a radial discontinuity resulting in errors at at least two points of the data frame. Such discontinuities remarkably reduce the rate at which address information or other additional information contained in the data frame can be detected.
A conventional method of recording address information by forming a wobbling groove in a disc type recording medium is disclosed in European Patent No. 1291857, filed on Mar. 12, 2003.